/**   
*
* @创建人：Liuyong   
* @创建时间：2013-11-12 下午09:36:32   
*    
*/ 
package com.crmsys.common.util;

import java.io.ByteArrayOutputStream;

/**   
 *
 * @描述：   解密加密数据
 * @创建人：Liuyong   
 * @创建时间：2013-11-12 下午09:36:32   
 * @修改人：Liuyong   
 * @修改时间：2013-11-12 下午09:36:32   
 * @修改备注：   
 * @version 1.0
 *    
 */
public class Decode64 {
	 private static byte[] decodeChars64 = new byte[] {   
		    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,   
		    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,   
		    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,   
		    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,   
		    -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,   
		    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,   
		    -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,   
		    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1 };   
		   
		    public static byte[] decode(String str) {   
		        byte[] data = str.getBytes();   
		        int len = data.length;   
		        ByteArrayOutputStream buf = new ByteArrayOutputStream(len);
		        int i = 0;   
		        int b1, b2, b3, b4;   
		    
		        while (i < len) {    
		            do {   
		                b1 = decodeChars64[data[i++]];   
		            } while (i < len && b1 == -1);   
		            if (b1 == -1) {   
		                break;   
		            }   
		              
		            do {   
		                b2 = decodeChars64[data[i++]];   
		            } while (i < len && b2 == -1);   
		            if (b2 == -1) {   
		                break;   
		            }   
		            buf.write((int) ((b1 << 2) | ((b2 & 0x30) >>> 4)));   
		               
		            do {   
		                b3 = data[i++];   
		                if (b3 == 61) {   
		                    return buf.toByteArray();   
		                }   
		                b3 = decodeChars64[b3];   
		            } while (i < len && b3 == -1);   
		            if (b3 == -1) {   
		                break;   
		            }   
		            buf.write((int) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));   
		               
		            do {   
		                b4 = data[i++];   
		                if (b4 == 61) {   
		                    return buf.toByteArray();   
		                }   
		                b4 = decodeChars64[b4];   
		            } while (i < len && b4 == -1);   
		            if (b4 == -1) {   
		                break;   
		            }   
		            buf.write((int) (((b3 & 0x03) << 6) | b4));   
		        }   
		        return buf.toByteArray();   
		    }
}
